1. Field of the Invention
The present invention relates to gravity-closing tongs for handling steel ingots, slabs, or similar loads. the inventive tongs are provided with two two-armed legs, each of which is pivotable about a horizontal pivot which is disposed transverse to the pivoting plane of the legs and is supported in a tongs housing. The lower arms are provided with gripping pins or similar devices, and the upper arms are hinged to equal-length links. The inventive tongs or grippers are also provided with adjusting means for axially displacing the pivots, and an accumultor to intensify the gripping force of the gripping pins.
2. Description of the Prior Art
In an earlier disclosure of tongs of the type initially referred to, the accumultor is a vertically arranged compression spring, which is loaded or tensioned by means of a pull-rod that is arranged to be lifted by a hydraulic cylinder. The compression spring of the present invention causes the gripping pins in the tongs legs to be pressed onto the ingot or slab with a greater force than is obtainable in the case of gravity-closing tongs without a compression spring; moreover, it permits additional shocks, which result from vertical forces, to be mitigated.
Where tongs are provided with means to adjust their opening, however, shock-like loads or stresses are liable to arise when the gripping centers or pins contact the load which is to be picked up. These loads or stresses, which are detrimental to the drive of the adjusting means, cannot be mitrigted by the previously known and disclosed vertical spring. Therefore, according to the previously known art, it would be necessary to provide separate features to mitigate these shocks (impacts), e.g. by providing a slip coupling or similar. However, this is not a subject which was discussed in the earlier disclosure in the German Patent 26 50 034 Kropik dated Nov. 22, 1979 and belonging to the assignee of the present invention. Thus, a drawback of the previously known tongs is increased complexity thereof, which is due to the need for a separate drive for loading the compression spring and to provide separate means to mitigate the shock or impacts that act on the drive of the adjusting means.
An object of the present invention is to provide gravity-closing tongs of the type described above to intensify the contact pressure of the gripping pins of the tongs and to mitigate the shocks or impacts acting on the drive of the adjusting means with a minimum amount of effort and complexity of design. It is a further advantage of the present invention that the complete tongs can be conveniently and easily separated from the load suspension device.